On Fri, Nov 27, 2015 at 04:02:39PM +0100, Patrik Hermansson wrote:
> This patch adds the option to specify virtio queue sizes. Currently the
> queue sizes is hard coded to 256, which might not be suitable for all types
> of applications.
Any more data here? 256 packets seems plenty. Is there a chance
your application does not support indirect descriptors?
That's a better approach I think.
> This patch makes it possible to specify the queue size between
> 256 to 1024.
>
> The minimum value is chosen based on the current sizes of the virtio
> queues. The maximum queue size is based upon VIRTQUEUE_SIZE_MAX.
To me, this seems excessive. For example, 1024 will break if we have to
add a virtio net header entry (on old kernels).
> ---
> hw/net/virtio-net.c | 31 ++++++++++++++++++++++++++++---
> include/hw/virtio/virtio-net.h | 8 +++++++-
> 2 files changed, 35 insertions(+), 4 deletions(-)
>
> diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
> index a877614..c4fcb39 100644
> --- a/hw/net/virtio-net.c
> +++ b/hw/net/virtio-net.c
> @@ -1326,20 +1326,40 @@ static void virtio_net_tx_bh(void *opaque)
> }
> }
>
> +static void virtio_net_validate_queue_limit(uint16_t *queue_size)
> +{
> + if (*queue_size > VIRTIO_QUEUE_SIZE_MAX) {
> + error_report("queue-size: %d, exceeds maximum allowed
> queue-size(%d),"
> + "queue-size set to %d", *queue_size,
> VIRTIO_QUEUE_SIZE_MAX,
> + VIRTIO_QUEUE_SIZE_MAX);
> + *queue_size = VIRTIO_QUEUE_SIZE_MAX;
> + } else if (*queue_size < VIRTIO_QUEUE_SIZE_MIN) {
> + error_report("queue-size: %d, below minimum allowed queue-size(%d),"
> + "queue-size set to %d", *queue_size,
> VIRTIO_QUEUE_SIZE_MIN,
> + VIRTIO_QUEUE_SIZE_MIN);
> + *queue_size = VIRTIO_QUEUE_SIZE_MIN;
> + }
> +}
> +
> static void virtio_net_add_queue(VirtIONet *n, int index)
> {
> VirtIODevice *vdev = VIRTIO_DEVICE(n);
>
> - n->vqs[index].rx_vq = virtio_add_queue(vdev, 256, virtio_net_handle_rx);
> + virtio_net_validate_queue_limit(&n->net_conf.rx_virtqueue_sz);
> + virtio_net_validate_queue_limit(&n->net_conf.tx_virtqueue_sz);
> + n->vqs[index].rx_vq = virtio_add_queue(vdev, n->net_conf.rx_virtqueue_sz,
> + virtio_net_handle_rx);
> if (n->net_conf.tx && !strcmp(n->net_conf.tx, "timer")) {
> n->vqs[index].tx_vq =
> - virtio_add_queue(vdev, 256, virtio_net_handle_tx_timer);
> + virtio_add_queue(vdev, n->net_conf.tx_virtqueue_sz,
> + virtio_net_handle_tx_timer);
> n->vqs[index].tx_timer = timer_new_ns(QEMU_CLOCK_VIRTUAL,
> virtio_net_tx_timer,
> &n->vqs[index]);
> } else {
> n->vqs[index].tx_vq =
> - virtio_add_queue(vdev, 256, virtio_net_handle_tx_bh);
> + virtio_add_queue(vdev, n->net_conf.tx_virtqueue_sz,
> + virtio_net_handle_tx_bh);
> n->vqs[index].tx_bh = qemu_bh_new(virtio_net_tx_bh, &n->vqs[index]);
> }
>
> @@ -1826,6 +1846,11 @@ static Property virtio_net_properties[] = {
> DEFINE_PROP_UINT32("x-txtimer", VirtIONet, net_conf.txtimer,
> TX_TIMER_INTERVAL),
> DEFINE_PROP_INT32("x-txburst", VirtIONet, net_conf.txburst, TX_BURST),
> + DEFINE_PROP_UINT16("rx_virtqueue_sz", VirtIONet,
> net_conf.rx_virtqueue_sz,
> + RX_VIRTQUEUE_SIZE),
> + DEFINE_PROP_UINT16("tx_virtqueue_sz", VirtIONet,
> net_conf.tx_virtqueue_sz,
> + TX_VIRTQUEUE_SIZE),
> +
> DEFINE_PROP_STRING("tx", VirtIONet, net_conf.tx),
> DEFINE_PROP_END_OF_LIST(),
> };
> diff --git a/include/hw/virtio/virtio-net.h b/include/hw/virtio/virtio-net.h
> index f3cc25f..dbcabbf 100644
> --- a/include/hw/virtio/virtio-net.h
> +++ b/include/hw/virtio/virtio-net.h
> @@ -28,13 +28,19 @@
> * ensures fairness in the io path. 256 conveniently matches the
> * length of the TX queue and shows a good balance of performance
> * and latency. */
> -#define TX_BURST 256
> +#define VIRTIO_QUEUE_SIZE_MIN 256
> +#define VIRTIO_QUEUE_SIZE_MAX VIRTQUEUE_MAX_SIZE
> +#define RX_VIRTQUEUE_SIZE VIRTIO_QUEUE_SIZE_MIN
> +#define TX_VIRTQUEUE_SIZE VIRTIO_QUEUE_SIZE_MIN
> +#define TX_BURST TX_VIRTQUEUE_SIZE
>
> typedef struct virtio_net_conf
> {
> uint32_t txtimer;
> int32_t txburst;
> char *tx;
> + uint16_t rx_virtqueue_sz;
> + uint16_t tx_virtqueue_sz;
> } virtio_net_conf;
>
> /* Maximum packet size we can receive from tap device: header + 64k */
> --
> 1.9.1
